Microcephaly

Definition and Diagnostic Criteria

• Fetal microcephaly is defined as:
  • Head circumference >2SD below mean or
  • Below the 3rd centile for gestational age
• Diagnostic standards vary:
  • Controversies about optimal reference charts and ethnic adaptations
  • Fetal charts differ from gestational-age adjusted postnatal charts
  • Fetal head circumference charts are not sex-specific